1. Field of the Invention
This invention relates to a power steering system including a torsion bar for sensing a steering force input.
2. Description of the Prior Art
Japanese patent publication 55-123566 discloses a power steering system including a torsion bar connected between an input shaft and an output shaft. Torsional displacement of the bar depends on the steering force input.
A control valve adjusts the hydraulic pressure applied to a power cylinder connected to a steering linkage. The control valve has a spool, the axial position of which determines the level of hydraulic pressure applied to the power cylinder. A transmission device connecting the torsion bar to the spool allows the spool to move axially in accordance with torsional displacement of the bar.
The input shaft extends through the spool which is annular. To allow smooth rotation of the input shaft relative to the spool without unwanted displacement of the spool in a direction perpendicular to its axis, it is necessary to severely limit the tolerances for the input shaft and the spool.
The number of parts of the transmission device is inconveniently large.